In recent years, images in a printing system accompanied with a dry electrophotographic system have been improved, and it has been utilized in a printing field for the comparatively small number of print copies. As a result, a desired image level is raised to such an extent that we have not conventionally understood it, and rare usage in the past, for example, printing onto a coated paper sheet, printing for high coverage images, printing for extremely high quality images and images exhibiting subtle tone (color tone), printing continuously for a large number of the same images, or the like has been in heavy usage. Thus, generation of failures which have not been mentioned at all is increased.
There appears one problem such as generation of interferential streaks in a halftone image seemingly originated by light exposure pattern and cutting frequency on the support surface of a photoreceptor. This is a problem which has been recurrently produced in recent years via combination of demand of improving evenness of intermediate color, performance improvement of image forming apparatuses and application for coated paper sheets, and has not been able to be handled by the conventional art.
In addition, this has conventionally responded to the foregoing problem by devising concave-convex profile on the support surface of the photoreceptor (for example, Patent Documents 1-3). The countermeasures disclosed therein might be those responding to failures regarded as the problems in the present invention. There is the limited effect, since periodicity itself in surface profile on the support of the photoreceptor, of course, remains, but produced has been the sufficient effect with respect to a quality level of images output onto plain paper sheets used at the office as main stream paper sheets. However, in the case of high image quality outputting images (output onto a coated paper sheet in the light printing field, for example) whose demand has been increased in recent years, the effect is insufficiently produced.
(Patent Document 1) Japanese Patent No. 3480618
(Patent Document 2) Japanese Patent Open to Public Inspection (O.P.I.) Publication No. 2003-91085
(Patent Document 3) Japanese Patent No. 3894023